Optimizing AA 5182 Alloy for High‐Speed Propeller Applications in Quasi‐Marine Environment: An Electrochemical and Erosion–Corrosion Analysis

Heat‐treated AA5182‐H321 was optimized for high‐speed propeller use by integrating a sacrificial Al–Mg interlayer and a diffusion‐resistant epoxy–polyurethane topcoat. Electrochemical testing and weight‐loss analysis demonstrated that the interlayer provided sacrificial‐anode‐based cathodic protection, while the topcoat limited oxygen and chloride ingress, mitigating intergranular corrosion of intermetallic principates and prevent erosion‐corrosion in simulated marine environment. Performance was evaluated under salt fog, rotating quasi‐marine immersion, and rotating abrasive environments. The H321 pretreatment homogenized β‐phase distribution and reduced intergranular corrosion, lowering weight loss compared with the as‐received alloy. Interlayers containing 20 wt.% Mg offered the most stable protection, with controlled sacrificial depletion across all conditions. Observed under‐interlayer corrosion confirmed the need for a barrier topcoat. The combined interlayer–topcoat system produced a noble shift (–0.9 to –0.5 ), reduced from to , and decreased mass loss to near‐negligible levels under immersion, salt spray, and erosion–corrosion exposure.